The clinical core isotope ratio mass spectrometry (IRMS) core laboratory was started to support all stable isotope applications in the clinical labs. Two isotope ratio mass spectrometers were installed in February 2009. One system can measure the isotope ratios of oxygen and hydrogen in water for energy expenditure applications. Methods for oxygen and hydrogen isotopic measurements have been developed and validated. Research has progressed towards the analysis of minute samples that may be able to analyze samples from animal studies. The second system is a GC-IRMS for metabolic studies. Initial metabolic studies will include labeled glucose, this method is currently under investigation.